Plastic resins are one of the most convenient materials and have been used widely in daily life since the 20th century. In addition, as mass production of plastic resins is realized due to development of the petrochemical industry, demand therefor is rapidly increasing and use of plastic resins is expanded from applications for daily life to applications for industry.
General-purpose resins were initially used mainly in daily necessities such as household goods, engineering plastics are mainly used ire applications for industry or manufacturing industry and, furthermore, super engineering plastics are used in specific fields, beyond satisfying required properties of materials for general industries and its market is continuously expanding.
As the automobile industry is focusing on more lightweight automobiles, demand for plastics is increasing in more various fields, and demand for polymer materials needed due to development of new technologies such as IT, semiconductors, electric vehicles, and the like is already growing in a variety of fields and is expected to be increasing more broadly in near future.
Recently, to address environmental problems due to generally used existing plastics, use of polyalkylene carbonates, which are aliphatic alkylene carbonates based on carbon dioxide generated as a byproduct gas, has drawn much attention.
Among these aliphatic alkylene carbonates, polypropylene carbonate (PPC) is prepared by polymerizing propylene oxide and carbon dioxide using a special catalyst. Currently, in the U.S., Novomer and Eastman Kodak are co-developing PPC as a packaging material with excellent oxygen-blocking properties, Japan's Sumitomo Chemical Co., Ltd is trying to enhance physical properties of PPC through complexation with other plastics, and, in particular, Tianquan and the like in China are commercially producing PPC thanks to active support from the Chinese government. However, productivity of PPC is limited due to deficiency in manufacturing technology, in particular catalyst technology. In South Korea, SK Innovation Co. Ltd has succeeded in production of carbon dioxide-based polymers by developing a catalyst technology capable of minimizing the amount of a cyclic carbonate and generating high molecular weight and, currently, a total of 16 institutions including enterprises, laboratories, universities, and the like are participating in “business for practical applications of green technology using byproduct gases” organized by Ulsan Technopark and are progressing development of eco-friendly products using carbon dioxide-based polymers and commercialization thereof.
Such polyalkylene carbonate (PAC) materials are advantageous in that PACs, such as polar polymers, e.g., ethylene vinyl alcohol (EVOH), nylon, and the like, have excellent barrier properties against gases and organic solvents and thus may be used as a packaging material for meat processed foods, industrial products, and the like. However, PACs having a glass transition temperature Tg of about 38 to 40° C. are easily brittle at Tg or less and are not suitable for use in independent molded products due to soft and sticky properties thereof at Tg or higher. Therefore, there is a need to develop technology for manufacturing a multilayer molded product using a PAC in combination with polyolefin, which is a general-purpose plastic, to complement these physical properties.
In general, when multilayer molded products are manufactured using a polar polymer such as EVOH, nylon, or the like and polyolefin, a polymer, which is prepared by copolymerizing a material selected from the group consisting of carboxylic acid, anhydrides, ester monomers, and the like onto a main chain or side chain of polyolefin or the like, is used to form an adhesive layer. A method of forming such an adhesive layer is disclosed in U.S. Pat. Nos. 4,206,967 and 3,953,655, and the manufactured multilayer molded products have high adhesive strength.
However, unlike existing base materials mixed with polyolefins, such as EVOH, nylon, and the like, to manufacture a multilayer molded product using polyalkylene carbonate and polyolefin. When the polymer prepared by copolymerizing or grafting a material selected from the group consisting of carboxylic acid, anhydrides, ester monomers, and the like onto a main chain or side chain of polyolefin or the like is used to form an adhesive layer, adhesion between the polymer and the polyalkylene carbonate is too low.
Therefore, there is an urgent need to develop a polyalkylene carbonate-based adhesive member with significantly enhanced adhesion to polyalkylene carbonate.